The feeding of birds by means of bird feeders is well known in the art. The bird feeders can range from simple tube type feeders to those having designs to permit the exclusion of heavier birds and/or marauders such as squirrels. Exemplary of the latter type of bird feeders are those shown in U.S. Pat. Nos. 6,543,384, 7,739,982 and 8,230,809, the teachings of which are hereby incorporated by reference.
Although the above mentioned bird feeders work as described therein, one of the problems associated with such bird feeders is the calibration of the spring mechanism. The spring mechanism is the means by which a shroud is moved to permit or deny access to the contents of the seed container. While some of the structures permit adjustment of the spring tension, others are fixed at a predetermined level.
As shown in some of these patents, a weight activated closure system is based on a tension spring system. The tension spring holds the shroud in an open position and is biased against the seed container assembly. Inherent in this design is the need for top and bottom stops to hold the spring under tension. The spring is tensioned and held in tension by the compression of the spring when the bird feeder components are assembled and fastened.